1. Field of the Invention
The present invention relates to nano-wire arrays, and more particularly, to a method of fabricating a nano-wire array, capable of implementing a large scale nano-wire array even when nano-wires are not arranged parallel to electrode lines by selectively etching the nano-wires on a substrate and patterning electrodes to be vertical to the electrode lines so as to increase the possibility of connecting the electrodes with the nano-wires.
The present invention has been produced from the work supported by the IT R&D program of MIC (Ministry of Information and Communication)/IITA (Institute for Information Technology Advancement) [2006-S-006-01, Components/Module technology for Ubiquitous Terminals] in Korea.
2. Discussion of Related Art
Since the advent of transistors in 1948 as an amplifying component using conductive activation in semiconductor crystalline organization, transistors have been widely being used in a variety of electronic applications. Especially, transistor arrays with pluralities of transistors are usefully employed in various fields such as memories or sensors.
FIG. 1 illustrates a cross-sectional view of a general metal-oxide-semiconductor field-effect transistor (MOSFET) and a disposition of DRAM cells in the form of a transistor array.
The left side of FIG. 1 shows a cross-sectional view of the MOSFET formed of a gate electrode coupled to a gate terminal (to which a gate voltage is applied), an insulating layer of SiO2, a semiconductor body (or semiconductor substrate), and drain and source each connected to drain and source terminals. With the structure of MOSFET, when a bias voltage is set to the drain and source while inducing a channel between the drain and the source by applying a gate voltage to the gate, the MOSFET is turned on by charge flow through the channel.
In the meantime, a capacitor that may be coupled to the drain of the MOSFET accumulates charges flowing into the source and stores information by charge accumulation when the gate voltage is cut off.
The right side of FIG. 1 shows a transistor array where unit cells are arranged to include MOSFETs and capacitors.
The transistor array is a DRAM cell array having a structure able to store information represented in the binary codes of ‘1’ and ‘0’ as data. In finding information stored in the transistor array, the gate voltage is applied to the gate to generate the channel. If the unit cell stores data ‘1’, charges flow out toward the source from the capacitor and then a sensor detects the charge flow to confirm the information.
With the recent development of semiconductor technology, MOSFETs are more scaled down and integrated than before. Specifically, since the discovery of a carbonic nano-tube by Iijima in 1991, numerous studies of nano-wires are being energetically conducted to improve the possibilities of practical applications and more advanced integrated circuits, by way of improving the patterning techniques using E-beam, ionic beam, X-ray, photolithography, and atomic force microscope (AFM).
It is impossible to identify a nano-wire with the naked eye because its diameter is less than several nano-meters and its length is several micrometers, but is visible through a specific instrument, such a scanning electron microscope (SEM). In order to use the nano-wires in an electronic device, it is necessary to align the nano-wires in a desired orientation. There are several ways of aligning the nano-wires, such as aligning the nano-wires by applying an electric field to a substrate, or laying the nano-wires along grooves formed in a substrate. As a way of directly fabricating a device without an additional step of aligning the nano-wires, there is a method of forming electrodes by means of the E-beam lithography along orientations of laying the nano-wires after finding the positions and orientations of the nano-wires by the SEM.
The nano-wires are not suitable for use in practical electronic devices or for mass-production, because they are insufficient in the characteristics of alignment selectivity and electromagnetism. Therefore, regularizing the nano-wires' orientation is one of important factors in the field of nano-tube technologies. Until now, even with various ways of aligning the nano-wires, a way of aligning the nano-wires in parallel along a united orientation has still not been proposed. Accordingly, it is difficult to mass-produce devices with the nano-wires.